Utilization of nanocomposite sensors for structural strain measurement has been widely studied. The basic mechanism of strain sensing is that a network formed by nanofillers is deformed in the presence structural strains, and such network deformation causes changes in the resistance value of a sensor formed by the nanofiller network. Thus, through resistance measurement, the levels of structural strains can be, in theory, captured and quantified.
There are many different types of nanofillers, including carbon nanotube (CNT), carbon black (CB), graphene, etc. The types of polymer matrix for housing nanofillers can also be chosen from a wide range, for example, polyvinylidene fluoride (PVDF) or polyvinyl chloride (PVC). The major advantages of nanocomposite sensors over other types of sensors, such as lead zirconate titanate (PZT) sensors, are that their material properties are with preferable flexibility, the material can be freely coated on tested structures with desired geometry, and the cost of manufacturing the nanocomposite sensors can be very low. Such features are of great importance for SHM because it provides a suitable way of achieve a satisfactory balance between the “sensing density” and the “sensor cost” It follows that a highly dense sensor network can be conveniently formed on a structural surface with a low cost, being able to identify damage at a micro scale.
However, existing nanocomposite sensors suffer from two major limitations: (1) limited studies of coating technologies that can be used to generate sensor networks fast and effectively; and (2) lacking of development in distributed sensor networks for guided-wave-based impact/damage identification. Therefore, further development is needed to promote the application of nanocomposite sensors in SHM.